#include<bits/stdc++.h>
using namespace std;
class Solution {
public:
	int search(vector<int>& nums, int target) {
		int l=0,r=nums.size()-1,ans=-1;
		while(l<=r)
		{
			int mid=l+(r-l)/2;
			if(nums[mid]<target)
			{
				l=mid+1;
			}
			else if(nums[mid]>target)
			{
				r=mid-1;
			}
			else {
				ans=mid;break;
			}
		}
		return ans;
	}
};
